A. muscles churn and mix the food with acids and enzymes
B. glands make 3 quarts of digestive juices each day
C. food leaves as a thick liquid called chyme
D. all of the above
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d. all of the above
- Correct: All of the statements are true regarding the stomach:
a. muscles churn and mix the food with acids and enzymes: The stomach has muscular walls that contract and relax to mechanically churn and mix food with gastric juices, including hydrochloric acid and various enzymes (such as pepsin) that aid in the digestion of proteins.
b. glands make 3 quarts of digestive juices each day: The gastric glands in the lining of the stomach produce gastric juice, which contains hydrochloric acid, enzymes (such as pepsinogen), mucus, and intrinsic factor. These glands collectively secrete about 2 to 3 liters (quarts) of gastric juice per day.
c. food leaves as a thick liquid called chyme: After mixing with gastric juices and undergoing partial digestion in the stomach, food is transformed into a semi-liquid mixture called chyme. Chyme is then gradually released from the stomach into the small intestine for further digestion and absorption.
Therefore, all of the statements accurately describe processes that occur in the stomach.
Therefore, the Correct Answer is D.
The small intestine possesses permanent folds along its length known as
A. plicae circulares
B. haustra
C. villi
D. intestinal crypts
The Correct Answer is A.A. plicae circulares
- Correct: The small intestine possesses permanent folds along its length known as plicae circulares, also called circular folds or valvulae conniventes. These folds are permanent transverse ridges of the mucosa and submucosa that project into the lumen of the small intestine. They increase the surface area for absorption and digestion by slowing the passage of chyme and increasing contact between chyme and the intestinal lining, facilitating nutrient absorption.
B. haustra
- Incorrect: Haustra are pouches or sacculations formed by the muscularis externa of the colon (large intestine), not the folds of the small intestine.
C. villi
- Incorrect: Villi are finger-like projections of the mucosa of the small intestine that extend into the lumen. While villi increase the surface area for absorption, they are not permanent folds along the length of the small intestine.
D. intestinal crypts
- Incorrect: Intestinal crypts, also known as crypts of Lieberkühn, are invaginations of the epithelium located between villi in the mucosa of the small intestine. They contain stem cells that continuously divide and give rise to new epithelial cells, helping to replenish the epithelial lining of the intestine. Crypts are not permanent folds along the length of the small intestine.
Which of these processes occurs throughout most of the alimentary canal?
A. ingestion
B. propulsion
C. segmentation
D. absorption
The Correct Answer is B.b) propulsion
- Correct: Propulsion is the movement of food along the length of the alimentary canal, from the mouth to the anus. This process occurs throughout most of the alimentary canal and includes both swallowing (deglutition) and peristalsis. Swallowing moves food from the mouth to the esophagus, while peristalsis involves rhythmic contractions and relaxations of smooth muscles in the walls of the digestive organs, pushing food forward through the esophagus, stomach, and intestines.
a) Ingestion: Ingestion refers to the intake of food into the mouth, which occurs at the beginning of the alimentary canal.
c) Segmentation: Segmentation involves the mixing and churning of food within certain regions of the digestive tract, particularly the small intestine. It does not occur throughout most of the alimentary canal but rather in specific areas where mechanical digestion and absorption are optimized.
d) Absorption: Absorption is the process by which nutrients and water are taken up from the digestive tract into the bloodstream or lymphatic system. While absorption occurs primarily in the small intestine, it also occurs in other parts of the alimentary canal, particularly in the large intestine, but it is not a continuous process throughout most of the alimentary canal like propulsion.
Where does the chemical digestion of starch begin?
A. mouth
B. esophagus
C. stomach
D. small intestine
The Correct Answer is A.a) mouth
- Correct: The chemical digestion of starch begins in the mouth. Salivary amylase, an enzyme secreted by the salivary glands, initiates the breakdown of starch molecules into maltose and other smaller carbohydrate molecules. This process begins as soon as food enters the mouth and continues as it is mixed with saliva during chewing and swallowing.
b) esophagus
- Incorrect: The esophagus is not directly involved in the chemical digestion of starch. It serves primarily as a conduit for the passage of food from the mouth to the stomach via peristaltic contractions.
c) stomach
- Incorrect: While some minor digestion may occur in the stomach due to the presence of salivary amylase from swallowed saliva, the stomach is not the primary site of starch digestion. Its acidic environment inhibits the activity of salivary amylase, so significant starch digestion does not occur there.
d) small intestine
- Incorrect: Starch digestion continues in the small intestine, primarily in the duodenum, but it does not begin there. Enzymes such as pancreatic amylase and brush border enzymes further break down starch into simpler sugars in the small intestine.
Which of these statements about bile is true?
A. About 500 mL is secreted daily.
B. Its main function is the denaturation of proteins.
C. It is synthesized in the gallbladder.
D. Bile salts are recycled.
The Correct Answer is D.d) Bile salts are recycled.
- Correct: Bile salts are recycled in the enterohepatic circulation. After aiding in the digestion and absorption of fats in the small intestine, bile salts are reabsorbed in the terminal ileum and transported back to the liver via the portal vein. Once in the liver, they are re-secreted into bile, allowing for their reuse in subsequent digestive processes. This recycling of bile salts is an important mechanism for conserving these critical components of bile.
a) About 500 mL is secreted daily.
- Incorrect: The daily secretion of bile by the liver is approximately 600-1000 mL, not 500 mL. Bile is continuously produced by hepatocytes (liver cells) and stored and concentrated in the gallbladder until it is released into the small intestine to aid in fat digestion.
b) Its main function is the denaturation of proteins.
- Incorrect: The main function of bile is not the denaturation of proteins. Bile aids in the emulsification and digestion of fats by breaking them down into smaller droplets, increasing the surface area for the action of pancreatic lipase and facilitating the absorption of lipids and fat-soluble vitamins.
c) It is synthesized in the gallbladder.
- Incorrect: Bile is not synthesized in the gallbladder. It is produced by hepatocytes (liver cells) in the liver and then stored and concentrated in the gallbladder until needed for digestion.
In which organ of the human body is urea produced as a result of the breakdown of amino acids?
A. liver
B. pancreas
C. stomach
D. small intestine
The Correct Answer is A.A) liver
- Correct: Urea is produced in the liver as a result of the breakdown of amino acids. Amino acids are the building blocks of proteins, and when proteins are metabolized for energy or other purposes, their constituent amino acids are broken down in a process called deamination. During deamination, the amino groups (-NH2) are removed from the amino acids, forming ammonia (NH3). The liver converts ammonia into urea through a series of biochemical reactions known as the urea cycle. Urea is then excreted by the kidneys in the urine, helping to remove nitrogenous waste from the body.
B) pancreas
- Incorrect: The pancreas is an organ involved in the production of digestive enzymes and hormones such as insulin and glucagon. It is not primarily responsible for the production of urea from the breakdown of amino acids.
C) stomach
- Incorrect: The stomach is primarily involved in the mechanical and chemical digestion of food, particularly proteins. While protein digestion begins in the stomach with the action of gastric juices containing enzymes such as pepsin, urea production from the breakdown of amino acids occurs mainly in the liver.
D) small intestine
- Incorrect: The small intestine is primarily involved in the absorption of nutrients from digested food, rather than the production of urea from the breakdown of amino acids. While some amino acids may be absorbed in the small intestine, urea production primarily occurs in the liver.
Which of these is most associated with villi?
A. haustra
B. lacteals
C. bacterial flora
D. intestinal glands
The Correct Answer is B.b) lacteals
- Correct: Villi are small, finger-like projections that extend into the lumen of the small intestine, increasing its surface area for absorption. Lacteals are specialized lymphatic vessels located within the villi. They play a crucial role in the absorption of dietary fats and fat-soluble vitamins. Lacteals absorb digested fats and fat-soluble nutrients and transport them through the lymphatic system to the bloodstream.
a) haustra
- Incorrect: Haustra are pouches or sacculations formed by the longitudinal muscle of the colon. They are characteristic features of the large intestine, particularly the colon, and are not directly associated with villi.
c) bacterial flora
- Incorrect: Bacterial flora (microbiota) refers to the diverse population of microorganisms inhabiting the gastrointestinal tract. While they play important roles in digestion, nutrient absorption, and immune function, they are not specifically associated with villi. They primarily inhabit the large intestine, where they aid in the fermentation of undigested carbohydrates and the production of certain vitamins.
d) intestinal glands
- Incorrect: Intestinal glands, also known as crypts of Lieberkühn or intestinal crypts, are invaginations of the epithelium located between the villi in the mucosa of the small intestine. They contain stem cells that continuously divide to replace the epithelial cells lining the intestine. While they are anatomically close to villi, they are distinct structures responsible for epithelial cell renewal and secretion of intestinal juices, but they are not directly associated with villi.
Chemical digestion of carbohydrates begins in the
A. esophagus
B. stomach
C. duodenum
D. oral cavity
The Correct Answer is D.D. oral cavity
- Correct: Chemical digestion of carbohydrates begins in the oral cavity. Salivary glands in the mouth secrete saliva, which contains an enzyme called amylase. Amylase breaks down complex carbohydrates (such as starch) into simpler sugars (such as maltose) through hydrolysis. This process initiates the digestion of carbohydrates before the food bolus reaches the stomach or small intestine.
A. esophagus
- Incorrect: The esophagus is primarily involved in the propulsion of food from the mouth to the stomach through peristaltic contractions. It does not play a significant role in the chemical digestion of carbohydrates.
B. stomach
- Incorrect: While the stomach plays a role in the digestion of proteins through the action of gastric juices containing pepsin and hydrochloric acid, it does not contribute significantly to the digestion of carbohydrates. In fact, the acidic environment of the stomach may temporarily inhibit the activity of salivary amylase.
C. duodenum
- Incorrect: The duodenum is the first part of the small intestine where the majority of chemical digestion occurs. While the duodenum receives pancreatic enzymes and bile that aid in the digestion of carbohydrates, proteins, and fats, the initial chemical digestion of carbohydrates primarily occurs in the oral cavity with the action of salivary amylase.
Pancreatic juice ________.
A. deactivates bile.
B. is secreted by pancreatic islet cells.
C. buffers chyme.
D. is released into the cystic duct.
The Correct Answer is C.c) buffers chyme.
- Correct: Pancreatic juice contains bicarbonate ions, which act as buffers to neutralize the acidic chyme entering the duodenum from the stomach. This neutralization is essential for maintaining the optimal pH for the activity of digestive enzymes in the small intestine.
a) deactivates bile.
- Incorrect: Pancreatic juice does not deactivate bile. Bile is not deactivated in the digestive process; instead, it aids in the emulsification and digestion of fats in the small intestine.
b) is secreted by pancreatic islet cells.
- Incorrect: Pancreatic juice is secreted by exocrine cells called pancreatic acinar cells, not by pancreatic islet cells. Pancreatic islet cells secrete hormones such as insulin and glucagon, which regulate blood glucose levels.
d) is released into the cystic duct.
- Incorrect: Pancreatic juice is released into the duodenum through the pancreatic duct, not the cystic duct. The cystic duct connects the gallbladder to the common bile duct, allowing bile to be released into the duodenum when needed for digestion.
Which of these statements about the pharynx is true?
A. It extends from the nasal and oral cavities superiorly to the esophagus anteriorly.
B. The oropharynx is continuous superiorly with the nasopharynx.
C. The nasopharynx is involved in digestion.
D. The laryngopharynx is composed partially of cartilage.
The Correct Answer is D.d) The laryngopharynx is composed partially of cartilage.
- True: The statement that the laryngopharynx is composed partially of cartilage is true. The pharynx, commonly known as the throat, is a muscular tube that extends from the base of the skull to the level of the sixth cervical vertebra. It serves as a passageway for both air and food. The pharynx is divided into three regions: the nasopharynx, oropharynx, and laryngopharynx.
a) It extends from the nasal and oral cavities superiorly to the esophagus anteriorly.
- False: The pharynx extends from the nasal and oral cavities superiorly to the esophagus and larynx inferiorly, not anteriorly.
b) The oropharynx is continuous superiorly with the nasopharynx.
- False: The oropharynx is continuous inferiorly with the oral cavity, not superiorly with the nasopharynx. The nasopharynx is continuous superiorly with the nasal cavity.
c) The nasopharynx is involved in digestion.
- False: The nasopharynx is primarily involved in respiration and the passage of air. It contains the openings of the auditory tubes and tonsils but is not directly involved in digestion.
Which of the following stimuli activates sensors in the walls of digestive organs?
A. breakdown products of digestion
B. distension
C. pH of chyme
D. all of the above
The Correct Answer is D.d) all of the above
- Correct: All of the listed stimuli activate sensors in the walls of digestive organs:
a) Breakdown products of digestion: The presence of breakdown products, such as nutrients and smaller molecules resulting from digestion, can activate sensors in the walls of digestive organs. These sensors help regulate various digestive processes and signal the release of digestive enzymes and hormones.
b) Distension: Distension, or stretching of the walls of the digestive organs, is a stimulus that activates sensors. It occurs as the volume of the digestive tract increases due to the presence of ingested food, and it triggers reflexes that coordinate muscular contractions for propulsion and mixing.
c) pH of chyme: The pH of the chyme (the semi-liquid mixture of food and digestive juices in the stomach and small intestine) is another stimulus that activates sensors. Changes in pH can signal the need for adjustments in the secretion of digestive enzymes and the regulation of gastric and intestinal functions.
Therefore, all of the mentioned stimuli play a role in activating sensors and regulating digestive processes in response to the specific conditions within the digestive organs.